C153705 Feasibility Study

• Contract/PO #: C153705
• Contractor Name: Beaver Reservoir Company
• Contract Type: Loan
• Water District: 59
• County: Gunnison
• Bill Number: SB 94-029
• Loan Projects - Doc Type: Feasibility Study

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A geotechnical investigation of the dam and foundation was conducted in July and
October of 1992 for collection of data to be used in this feasibility study. The
investigation consisted of drilling and sampling of four test holes, installation of four
standpipe piezometers, collection of self-potential (SP) geophysical data along five
transects and geotechnical laboratory testing of selected samples. The investigation
program is described in the February 4, 1993 WCCreport titled "Geotechnical
Investigation, Beaver ReselVoir Dam" (WCC, 1993). A copy of this report is included
in Appendix E for reference.

Inflows during the spring of 1993 were sufficient to fill the reselVoir and resulted in
releases through the emergency spillway on the right abutment during early June. The
temporary sinkhole caps installed the previous fall were inundated starting in May 1993
and were expected to remain so until drawdown in August or September. Inspection
reports by representatives of the BRC lmd the Colorado Division of Water Resources
(PWR) indicate that the temporary caps are effectively reducing underseepage based
on visual assessments of seepage" cjuafltitie~, downstream of the dam. In addition,
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piezometric data in the dam foundation,'collecte~.by BRC and summarized by DWR,
indicates that the zone of saturation remains below the embankment/foundation contact.
The piezometric data and se~page obselVations are summarized in the August 2, 1993
report by the DWR titled :'Follow-Up Inspection, Beaver ReselVoir" (CDWR, 1993). A
copy of this report is included in App~1]cdixF for reference.

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1.2 FEASIBILITY STUDY OBJECTIvE

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The objective ,onhis fea.sibilitystudy is to develop a preferred remedial alternative for
mitigation .of the underseepage and sinkhole development at Beaver ReselVoir.
Successfu.! 'J-epair will result in reduction or elimination of storage restrictions thereby
increasing 'ihe,,9ulU!tity.ofwater stored llnd available for irrigation.

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23067/R 1.1 09-03-93(3: 18pm)/RPT

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